Plant Phenolics Production: A Strategy for Biotic Stress Management

Phenolic compounds (polyphenols/phenolics) are the plants’ secondary metabolites produced for defense purposes. The ubiquitous nature of phenolics describes their functional diversity. They have noteworthy impact on different physiological and metabolic processes of plant. These compounds act as antimicrobial, antifungal, and antioxidant agents that intercept microbial invasions. Phenolics also play structural role in plants and provide integrity, vigor, and vitality to plant cells. Plant phenolic defense system includes physical alterations (suberization or lignification), metabolic changes (de novo biosynthesis of pathogenesis-related proteins), synthesis, and accretion of phenylpropanoid-derived metabolites (phytoalexins). Phenolics have dual function and act as both attractants and repellents for organisms around plants. They protect plants from the damage caused by pathogens and other microbes. Phenolic compounds have various defensive mechanisms that provide shield to plants for invading pathogens. Moreover, being weak acids, phenolics such as anthocyanins, hydroxycinnamic acid (HCAs), and flavonoids have free radicals scavenging potential that is accumulative in plants under stress and prevents plants from oxidative stress. In addition, phenolic compounds such as flavonoids are an important rhizospheric signaling molecules that attract symbiotic (Rhizobium) as well as pathogenic microbes (Agrobacterium). Thus, they are important in developing plant–microbial interactions.